The file "log" should now contain some debugging info. Send it to me (gerard.lledo@gmail.com), create a issue in github or simply post it here.

Get sure you are using at least OSX 10.5 with intel (ppc won't work). Also, I've only tested this with native ext4 partitions (no ext3 to ext4 upgrades), so it might give you problems if you have the later scenario.

I've tested and work 100% in ext4 partition in MACOSX 10.6.7,
a trick, to be read and save, use the command fuse-ext2 /dev/disk0sX /Volumes/linux -o force
or reboot macosx before installation and auto mount ext4 in macosx.